gypsum - sand selenite rose from a dry lake near Oujda, Morocco - large hand/display specimen This particular volcanic igneous rock

This particular volcanic igneous rock is composed of volcanic ash and many fragments (clasts) of other igneous rocks that were ejected from a volcanic vent

aragonite CaCo3

particularly in analytical chemistry

It would be instructive for students to compare these two dune sands - both fine-grained but very different in color

gypsum - sand selenite rose from a dry lake near Oujda, Morocco - large hand/display specimen This particular volcanic igneous rockSelenite gypsum sand rose CaSO4 2H2O Selenite gypsum sand roses form in seasonal desert lakes as they dry. Selenite is typically transparent, but when it crystallizes in sandy conditions it forms rosettes of flattened crystals, the rose petals, which are either encrusted with sand or with sand embedded throughout. The color of the gypsum crystals depends on the color of the sand in that dry lake. These Moroccan examples are particularly attractive.